Railway signaling system



Nov. 18, 1941. H. A. THOMPSON RAILWAY SIGNALING SYSTEM IN NTOR AbwardAf .NNN

H16 ATTORNEY Patented Nov. 18, 1941 RAILWAY SIGNALING SYSTEM Howard A. Thompson, Edgewood, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application February 7, 1940, Serial No. 317,717

8 Claims. (Cl; 246-34) My invention relates to railway signaling systems of the type having track circuits'employing coded or periodically interrupted current.

It has heretofore been proposed to provide means operable in the event an insulated joint separating two track sections is defective to establish a lockout circuit to supply steady uncoded energy to the section in the rear of the defective joint so that this energy will feed over the defective joint and maintain the track relay of the section in advance of the defective joint constantly energized to thereby cause the signal controlled by that track relay to display its most restrictive indication.

One mean for accomplishing this result is shown in my copending application Serial No. 210,743, filed May 28, 1938, for Railway traffic controlling apparatus.

It is an object of my invention to provide a railway signaling system incorporating an improved lockout circuit.

A further object of my invention is to pro-- vide an improved railway signaling system having a lockout circuit, the system being arranged to provide more certain assurance that if for any reason the lockout circuit is improperly interrupted it will be automatically reestablished.

Another object of my invention is to provide a railway signaling system incorporating a lockout circuit, the system being arranged so that none of the relays employed therein are energized by current supplied over circuits which include their own back contacts.

A further object of my invention is to provide an improved signaling system incorporating decoding apparatus including a transformer the primary winding of. which is supplied with current by a circuit including a contact of a code following relay, the system being arranged so that the transformer primary winding is supplied with current when and onlywhen the contacts of the code following relay are responding to coded energy to thereby eliminate current consumption by said transformer winding at times when the relay contacts are not responding to coded energy.

Another object of my invention is to provide a railway signaling system employing coded or periodically interrupted energy in thetrack circuits thereof, the system being arranged so that on entrance of a-train into a track section and shunting of the track relay there is no possibility that coded energy will be improperly supplied to the adjacent section in the rear.

A further objectlof the invention is to provide an improved signaling system of the type described, the system being arranged so that on shunting'of the track relay for a period long enough to effect release of one of the auxiliary relays controlled thereby, all of the auxiliary relays associated with the track relay will thereafter quickly become released, and so that until all of the auxiliary relays do become released energy will not be supplied to the adjacent section in the rear.

Other objects of my invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawing. I shall describe one form of railway signaling apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In'the accompanying drawing, the single figure .is a diagrammatic View showing a railway signaling system embodying my invention.

Referring to the drawing, ther is shown therein a pair of track rails l and 2 forming a stretch of railway track over which trafiic normally moves in the direction indicated by the arrow, that is, from the left to right. The rails of the track stretch are divided by insulated joints 3 into the customary successive track sections, and the rails of each of these sections form apart of a track circuit of the usual character.

The particular track stretch which is represented in the drawing is intended for use in a railway system employing electric current for propulsion purposes, and for this reason alternating current track circuit energy is used, together with impedance bonds 4 of the customary form which conduct propulsion current around each pair of insulated rail joints. As the description proceeds, however, it will be apparent that apparatus embodying my invention is equal ly well suitedfor use on a steam road in which case either direct or alternating current track circuit energy for the control of the signals may be employed. In such cases the impedance bonds 4 would, of course, be omitted.

In the drawing portions of two track sections are shown, these being identified as sections HT and I2T. Each of these sections has located at the entrance end thereof a signal'for governing movement of trains in the track stretch, the signal for section I2T being identified as 128. The signal illustrated is of the familiar color. light type having a green or proceed lamp G, a yellow or caution lamp Y, and a red or stop lamp R.

The rails of each of the track sections form a track circuit to which coded alternating current signal control energy is supplied at the exit or leaving ends from the secondary of a track transformer. The circuits for supplying current from the secondary windings of the track transformers include the usual current limiting reactors 6. The energy supplied to the track circuits is derived from any suitable source and may be distributed throughout the track stretch by a transmission line, not shown. In the drawing the terminals BX and CK designate the terminals of such power supply source, and it will be assumed that the energy supplied from the source is alternating current with a frequency of 100 cycles per second.

Each of the signal locations has associated therewith a suitable source of direct current, such as a primary or storage battery, not shown, the terminals of which are identified in the drawing by the reference characters B and C.

The particular signaling system shown in Fig. 1 is of the three indication variety and it makes use of track circuit energy of two different codings. This coded energy is provided by code transmitters CT associated with each track relay which interrupt the supply circuit of the associated track transformer a definite number of times a minute according to trafilc or other conditions ahead. In the illustrative form shown each code transmitter CT is provided with two circuit making'and breaking contacts and I80 which are continuously actuated by a motor or other suitable mechanism at two different speeds. For purposes of illustration it will be assumed that these speeds are such as respectively to provide 75 and 180 energy pulses per minute which are separated by periods of equal duration in which no energy is supplied.

Each of the track sections includes a code following track relay designated TR. together with an appropriate prefix. The track relay is located at the entrance end of the track section and may be of any suitable type. As shown, the relay is of the direct current type, having its winding connected to the track rails of the associated track section through a suitable resonant unit RU shown diagrammatically in the drawing.

The resonant unit I2RU comprises a transformer, a capacitor, and a reactor so arranged and proportioned as to freely pass the 100 cycle coded signal control energy, but so as not to pass propulsion current of a different frequency, while a rectifier is incorporated in the unit to convert into direct current the alternating current which is supplied through the unit.

The track relay I 2TB has associated therewith several auxiliary relays including a front contact repeater relay I ZFSA, a back contact repeater relay I2BSA, and two signal control relays I2H and I2J. Each of the other signals in the track stretch has associated therewith equipment corresponding to that associated with signal IZS.

The track relay contact 16 controls the supply of energy to the windings of the auxiliary relays IZFSA, I2BSA and I2I-I. When the track relay is responding to coded energy, the contact l6, when picked up, establishes the circuit for supplying energy to the winding of relay H, this circuit being traced from terminal B of the source of current through front contact I6 of track relay IZTR, front contact l8 of relay IZBSA, and winding of relay IZH to terminal C. A snubbing resistor is connected across the terminals of the winding of the relay IZH to render the relay contacts slow in releasing.

When the track relay is responding to coded energy the contact l6, when released, establishes the circuit to supply energy to the winding of relay IZBSA, this circuit being traced from terminal B of the source of current through back contact iii of track relay IZTR, front contact 2| of relay I2FSA, and winding of relay IZBSA to terminal C of the source of current.

A snubbing resistor 22 is connected across the terminals of the winding of relay IZBSA as long as contact 21 of relay IZFSA is picked up to render the contacts of relay IZBSA slow in releasing, and to insure prompt release of the contacts of the relay IZBSA on release of the contact 2| of relay IZFSA.

As long as the contacts of the relay 12H are picked up the winding of relay I2FSA is energized by current supplied over a circuit which is traced from terminal B of the source of current through front contact 24 of relay l2I-I, resistor 25, and winding of relay IZFSA to terminal C of the source of current.

Contact 24 of the relay IZH when picked up also establishes connection from terminal B of the source of current to contact [5 of track relay IZTR so that as long as the track relay responds to coded energy contact [5 alternately establishes circuits to energize the upper and lower portions of the primary winding 26 of the decoding transformer IZDT. The center terminal of the winding 26 is connected to terminal C of the source of current, while energy induced in the secondary winding 21 of the transformer IZDT is supplied through the resonant unit IZRUA to the winding of the relay IZJ.

The resonant unit |2RUA includes an inductance and a capacitor which are arranged and proportioned so that when the frequency of the current supplied to the unit is that which is present when the track relay IZTR is responding to energy of the code frequency sufficient current is supplied through the unit to pick up the contact of the relay IZJ. The resonant unit is also arranged so that when it is supplied with current of the frequency present when the track relay is responding to energy of a different code frequency, such as 75 code frequency, insuflicient energy is supplied to the relay IZJ to maintain the relay contact picked up. The resonant unit IZRUA includes a rectifier which rectifies the current which is supplied through the unit to the relay I2J.

.The relays IZFSA, IZBSA and IZH cooperate in the manner hereinafter described in detail to control the supply of energy to the primary winding 30 of track transformer HTT, while the relays IZH and I2J cooperate to control the circuits of the lamps G, Y and R of signal IZS.

The equipment is shown in the condition which it assumes when the track stretch is vacant for at least one section in advance of section |2T so that energy of the 180 code frequency is supplied to the rails of section IZT, and thus to the winding of track relay I2TR. Since the relay IZTR is responding to energy of the 180 code frequency, all of the auxiliary relays associated therewith are energized and the green lamp G of the signal I 28 is illuminated, while energy of the 180 code frequency is supplied to the track transformer IITT, and thereby to the rails of section I IT.

At this time the windings of the relays IZFSA, IZBSA and IZH are energized by current supplied over the circuits traced above, while the relay I2J is energized by current supplied through the resonant unit IZRUA.

As the relays 12H and I2J are energized the contacts of these relays are picked up and the green or clear lamp G of signal IZS is lighted by energy supplied over the circuit which is traced from terminal B of the source of current through front contact 32 of relay [2H, front contact 33 of relay IZJ, and lamp G to terminal C of the source of current.

As the contacts of the relays IZFSA, IZBSA and IZH are picked up energy of the 180 code frequency is supplied to the tracktransformer i ITT over the circuit which is traced from terminal BX of the source of signal control current through contact I80 of the code transmitter IZCT, front contact 35 of relay IZH, front contact 31 of relay IZBSA, and front contact 38 of relay IZFSA to one terminal of the transformer primary winding 30, the other terminal of which is connected to terminal CX of the source of signal control current.

Normal operation of the system on passage of a train When a train moving in the normal direction of traflic, that is from left to right, enters the section I2T, it shunts the track relay IETR and the contacts of this relay thereafter remain in their released position. On movement of contact IE to the released position it establishes the circuit for energizing the winding of relay IZBSA, and this circuit is complete as long as contact 2| of relay IZFSA remains picked up.

As track relay contact It remains in the released position and does not periodically engage its front contact, no energy is supplied to the winding of relay IZH, and after .a brief time in terval, the length of which is determined by the release time of the contacts of relay l2I-I, the contacts of this relay become released and contact 24 interrupts the circuit for energizing the winding of relay IZFSA, and also interrupts the circuit for establishing connection from terminal B of the local source of direct current to contact 15 of the track relay IZTR.

Upon disengagement of contact 24 of relay H from its front contact to thereby interrupt the circuit of the Winding of relay I2FSA and of the lower'portion of the decoding transformer primary winding 26, each of these windings has a current induced therein, and the two windings are arranged and proportioned so that these currents are substantially equal in magnitude and opposite in relative polarity. At this time the two windings are connected in a circuit which is traced from one terminal of the winding of relay I2FSA, which terminal is connected to terminal C of the source of current, through the re lay winding, resistor 25, contact l5 of track re" lay IZTR, and lower half of the transformer primary winding 26 to terminal C of the source of direct current, and, therefore, to the terminal movement into engagement with its backpoint of contact.

When contact 24 engages its back point of contact, the circuit for connecting the winding of relay I2FSA and the lower portion of the transformer primary winding 26 in series is altered by the establishment of connection of said circuitat of the winding of relay I2FSA which is also connected to terminal C.

Since the induced currents in the two windings are substantially equal in magnitude and opposite in polarity, the current from the transformer winding offsets or neutralizes that in the relay winding with the'result that the contacts of the relay IZFSA quickly become released. if the current induced in the relay winding were not neutralized or offset by the current from the transformer winding, release of the relay contactswould be delayed until after the current induced in the relay winding had died down, but

in this system as the current in the relay winding 1 is ofiset by that in the transformer Winding, re-' lease of the relay contactstakes place very quickly so that the contacts of the relay IEFSA will be disengaged from their front points of contact before contact 24 of relay 12H completes its a point therein intermediate the two windings with terminal C of the source of direct current.

This changes the series connection of the two.

windings to connection of both terminals of each winding to the same conductor, that is, to terminal C of the source of current, so that both windings are short circuited. When the relay winding is short circuited, any current remaining in the winding is dissipated, while the relay contacts thereafter complete their movemen-t to the released position, if they are not already in that position.

On release of the contact 2| of relay IZFSA the circuit for energizing the winding of relay IZBSA is interrupted, and, in addition, the circuit for connecting the snubbing resistor "22 across the terminals of the winding of relay IZBSA is interrupted so that the contacts of the relay IZBSA thereafter quickly become released.

As a result of the release of contact 35 of relay IZH, the circuit for supplying energy of the 180 code frequency to thev primary Winding 30 of track transformer H'IT is interrupted, while on movement of contact 31 of relay IZBSA into engagement with its back point of contact, the circuit for supplying energy of the code frequency to the transformer primary winding 36 is established.

The circuit for supplying energy of '75 code frequency to the transformer I ITT is traced from terminal BX of the source of signal control current through back contact 31 of relay IEBSA, and contact 15 of code transmitter CT to one terminal of the transformer primary winding 30.

It will be seen that in the interval between the release of contact 2'4 of relay 12H, which relay, 0n shunting of the track relay, is the first relay in the series of auxiliary relays to release its contacts, and the release of contact 31 of re lay IZBSA, which relay is the last in the series of auxiliary relays to release its contacts, no circuit or connection 'is established from terminal BX of the source of signal control current to the wire leading to the track transformer PIT. Accordingly, there is no possibility that during the release of the contacts of the auxiliary relays associated with the track relay energy will be improperly supplied to the track transformer IITT.

As a result of the release of the contact 32 of relay I2H, the circuit for energizing the green lamp G of the signal I23 is interrupted, while on movement of contact 32 into engagement with its back point of contact the circuit for energizing the red or stop lamp R is established, and this lamp becomes illuminated to indicate the section 1 2T is occupied.

It will be seen that when the track section is occupied the relay IZH is deenergized and its contact 24 is released, thereby interrupting the circuit of the track relay contact l5 so that no energy is supplied to the transformer primary that described in detail above so that the energy supplied to the rails of section I2T is changed from 180 code frequency to 75 code frequency. As long as any portion of the train remains in section I2T, the track relay IZTR continues to be shunted, but when the rear of the train passes out of section I2T, the energy of '75 code frequency supplied to the rails of section |2T feeds to the track relay IZTR, and the contacts of this relay are thereafter picked up and released in response to this energy.

On the first movement of the contact l6 of track relay I2TR to its picked up position a circuit is established to energize the winding of track relay IZFSA and the contacts of this relay thereupon become picked up. The circuit for energizing the winding of relay I2FSA is traced from terminal B of the source of current through front contact l6 of relay I ZTR, back contact l8 of relay IZBSA, and winding of relay IZFSA to terminal C of the source of cur rent.

In addition, at this time a circuit is complete through the resistor 25 between the terminals B and C of the source of current. This circuit is traced from back contact l8 of relay I ZBSA, through resistor 25, and back contacts 24 of relay IZT to terminal C.

The period during which this circuit is complete is relatively short, the circuit being interrupted on the next released period of the track relay contact l6, while current flow in the circuit is limited by the resistor 25 so that the current consumption is inconsequential.

On picking up of contact 38 of relay I2FSA a circuit is established which shunts the 75 code contact of code transmitter I2CT so that steady energy is supplied to the track transformer I I TT, and therefore to the rails of section HT.

In addition, on picking up of contact 2! of relay IZFSA a circuit is established to energize the winding of relay IZBSA on movement of the track relay contact IE to its released position.

On the first movement of contact I6 of relay IZTR to the released position the circuit for energizing the winding of relay IZFSA is interrupted, but a snubbing circuit shunting the winding of this relay is complete at this time so that the contacts of this relay are rendered slow in releasing and remain picked up for a time interval.

The snubbing circuit shunting the winding of relay IZFSA is traced from terminal C of the source of current through the winding of the relay, resistor 25, and back contact 24 of relay IZH to terminal C of the source of current, which is the same terminal to which the other terminal of the relay winding is connected.

On the first movement of the track relay contact IE to the released position following its first period in the picked up position, energy is supplied to the winding of relay I2BSA over the circuit which is traced from terminal B of the source of current through back contact l6 of relay IZTR, front contact 2| of relay IZFSA, and winding of relay IZBSA to terminal C of the source of current.

As a result of the supply of energy to the relay winding, the contacts of the relay |2BSA become picked up, and as the snubbing resistor 22 is connected across the terminals of the relay winding at this time, the contacts of the relay are rendered slow in releasing and remain picked up during the subsequent picked up periods of the track relay contacts.

On picking up of the contacts of relay IZBSA contact 31 interrupts the circuit for supplying steady energy to the transformer I I TT, and establishes the circuit through which energy of the code frequency is supplied to the transformer llTT after the contacts of relay |2H become picked up.

On picking up of contact l8 of relay IZBSA the circuit for energizing the winding of relay IZFSA is interrupted, and a circuit is established to energize the winding of relay IZI-I during subsequent picked up periods of the track relay contact l6.

Accordingly on the next or second picked up period of the contact [6 of relay I2TR energy is supplied to the Winding of relay IZI-I over the circuit which is traced from terminal B of the source of current through front contact I6 of relay IZTR, front contact l8 of relay IZBSA, and winding of relay IZH to terminal C of the source of current.

.As a result of the supply of energy to the winding of relay [21-1 the contacts of this relay become picked up, while on movement of the contact 24 of relay I2H out of engagement with its back point of contact additional resistance is connected in the snubbing circuit of the relay I ZFSA to insure that the contacts of that relay will remain picked up until contact 24 of relay IZH completes its movement to the picked up position, at which time a circuit is established to supply energy to the winding of relay IZFSA to maintain the contacts of that relay picked up.

On movement of contact 24 of relay I2H out of engagement with its back contact the connection of resistor 25 directly to terminal C of the source of current is interrupted, while resistor 25 is connected to terminal C through track relay'contact l5 and the upper portion of the primary winding 26 of decoding transformer IZDT so that the resistance of the snubbing circuit of the relay IZFSA is increased by the value of the resistance of the portion of the transformer primary winding which is added to the circuit.

On movement of the contact 24 of relay I2H to its picked up position a circuit is established from terminal B of the source of current through resistor 25 to one terminal of the winding of relay IZFSA with the result that the winding of the relay is energized, and thereafter the contacts of relay IZFSA are held picked up as long as the contacts of relay 12H are picked up.

It Will be seen that during the period in which contact 24 is in transit between its front and back points of contact direct connection from resistor 25 to terminal C of the source of current is interrupted, but that at this time another connection is present from resistor 25 to terminal C of the source of current. This oth'er connection provides increased resistance in the snubbing circuit for the winding of relay IZFSA and serves to prevent release of the relay contacts until contact 24 completes its movement to its picked up position to supply energy to the winding of relay IZFSA. The snubbing circuit which includes the portion of the primary winding of the decoding transformer IZDT is not very efficient, but is eifective enough to maintain the contacts of relay IZFSA picked up during the very short time interval required for the contact 24 of relay l2I-I to move between its two positions.

As a result of the supply of current to the winding of relay I ZFSA over the circuit established by contact 24 of relay I 2H, the contacts of the relay IZFSA are held picked up so that the circuit for energizing the relay I2BSA during the released periods of the track relay contact I6 is complete, while as the contacts of relay lZBSA are thereafter maintained picked up, the circuit for energizing the Winding of relay I2H during the picked up periodsof the track relay contact is also complete. Accordingly as long as the contacts of relay IZTR continue to follow code, the windings of relays IZBSA and HE are alternately energized and the contacts of these relays are maintained picked up, while the circuit is maintained to energize the Winding of relay IZFSA.

On picking up of contact 24 of relay [2H connection is established from terminal B of the source of current to contact I of the track relay IZTR. Accordingly on code following operation of contact l5 of the track relay subsequent to picking up of the contacts of relay [211 the two portions of the primary winding 26 of the decoding transformer IZDT are alternately energized and current is induced in the secondary winding 21. Sincethe track relay IZTR is responding to energy of the 75 code frequency at this time, the freque cy of the energy induced in the secondary Winding 2! is such that the resonant unit IZRUApasses too little current to effect picking up of the contact of relay I2.) and the contact of that relay therefore remains released.

Since at this time the contacts of relay [2H are picked up, a circuit is established to illuminate the yellow or caution lamp Y of signal IZS, this circuit being traced from terminal 3- of the source of current through front contact 32 of relay l2I-I, back contact 33 of relay I2J, and lamp Y to terminal C of the source of current. At this time energy of the 180 code frequency is supplied to the track transformer IITT over the circuit traced above.

When the train has advanced far enough in the track stretch to vacate the section in advance of section I2T, the equipment associated with that section operates in the manner described in detail in connection with section [2T to supply energy of the 180 code frequency instead of energy of the '75 code frequency to the rails of section IZT.

On this change in the frequency of the impulses of current supplied to the track relay IZ'I'R, the contacts of this relay are picked up and released at the higher speed, while the frequency of the current supplied by the transformer secondary Winding 21 is such that the resonant unit I2RUA passes suflicient current to effect picking up of the contact 33 of relay IZJ.

As a result of the picking up of contact 33, the circuit for illuminating the yellow lamp Y is interrupted, and the circuit is established to illuminate the green lamp G of the signal HS.

Operation of equipment if an insulated jointbreaks down as a result of passage of a tram For purposes of illustration it will be assumed that an insulated joint 3 separating sections HT and IZT breaks down as a result of passage of a train, and the operation of the equipment under such conditions will now 'be considered.

In electrified territory because of the wellknown operation of the impedance bonds 4, breaking down of one insulated joint has the same effect as breaking down of both insulated joints in steam propulsion territory, and permits the impulses of signal control current supplied to the section in the rear of the defective joint to feed to the track relay of the section in advance of the defective joint.

When a train moving from left to right enters section IZT, it shunts the track relay IZTR and the contacts of this relay remain in their released positions with the result that the winding of relay IZH is deenergized and the contacts of that relay become released, thereby interrupting the circuits of the winding of relay IZFSA and of the primary winding 26 of decoding transformer IZDT. Accordingly the contacts of relay IZFSA quickly become released, as explained above, thereby interrupting the circuit of the winding of the relay IZBSA so that the contacts of that relay become released.

circuit for illuminating the red lamp R of signal [28 is established, while on release of contact 35 of relay [2H the circuit for supplying energy of the code frequency to the transformer IITT is interrupted.

As a result of the release of the contacts of relays IZFS A and IZBSA, the circuit traced above for supplying energy of the 75 code frequency to the transformer IITT is established.

When the rear of the train vacates section HT, energy supplied to the rails of section IIT will feed over the defective insulated joint to the rails of section I2T, but the shunting action of the wheels and axles of the train will prevent effective energization of the winding of the track relay IZTR until the train has advanced far enough in the track stretch for the rear of the train to be located some distance in advance of the track relay.

When the train has advanced this far in the track stretch, the impulses of current supplied by transformer IITT to the rails of section HT, and feeding over the defective joint, will effect picking up of the contacts of relay IZTR.

On the first picked up period of the contacts of the track relay IZTR. energy is supplied to the winding of relay IZFSA over the circuit which includes front contact [6 of the track relay and back contact I8 of relay IZBSA.

As a result of the supply of energy to the winding of relay IZFSA, the contacts of this relay become picked up and contact 38 establishes the circuit shunting the 75 code contact of code transmitter IZCT with the result that the lockout or steady energy supply circuit is complete, and steady uncoded energy is supplied to the track transformer IITT over the circuit which is traced from terminal BX of the source of signal control current through back contact 31 of relay IZBSA, front contact 38 of relay I'ZFSA, and winding 30 of transformer IITT to terminal CX of the source of current.

As steady uncoded energy is supplied to the track transformer IIT'I this transformer supplies steady uncoded energy to the rails of section I IT, and this energy feeding over the defective. insulated joint will maintain the contacts of track relay IZTR constantly picked up, and, accordingly, no energy is supplied to the winding of relay I2BS'A and the contacts of that relay remain released so that the steady energy or lockou circuit is maintained.

In addition at. this time the relay l2I-I remains deenergized. and its contact 32 remains released so that the red or stop lamp R of signal IZS is illuminated.

the rails of section HT, the track relay of that section is steadily energized and the signal for that section is conditioned to display its red or stop aspect.

When the train has advanced far enough in the, track stretch so that the rear of the train vacates section IZT, the impulses of energy supplied by the equipment associated with the track relay for the section in advance will feed t the track relay IZTR, but since the intervals between impulses of current are filled in by the steady energy feeding over the defective joint, the supply of these impulses to the track relay IZTR. will be without effect and the contacts of relay IZTR will be held steadily picked up.

From the foregoing it will be seen that in the event an insulated joint becomes defective as a result of passage of a train, the system provided by this invention operates to supply steady uncoded energy to the section in the rear of the defective joint to thereby prevent the improper display of a proceed indication by the signal for the section in advance of the defective joint.

Operation of equipment if an insulated y'oint breaks down as a result of passage of a light 7 weight high speed train As explained above if an insulated joint becomes defective as a result of passage of a train the equipment will operate to establish the lockout circuit to prevent the improper display of a proceed aspect by the signal for an occupied section.

The sequence of operation outlined above will take place where the train which breaks down the joint is of normal weight, length and speed. However, where the train which renders the joint defective is short, light weight and high speed special problems are encountered, and the system provided by this invention is arranged to insure that under such conditions the lookout circuit will be established.

A train which is short and fast will soon ad- Vance far enough in a track section to be ineffective to shunt the track relay of the section with respect to energy feeding to the track relay over a defective insulated joint from the adjacent track section in the rear.

If the train advances beyond the point at which it is effective to shunt the track relay with respect to energy supplied from the section in the rear before all of the auxiliary relays associated with the track relay have become released, there is a possibility that in the systems heretofore provided that the lockout circuit will not be established, and that energy of 180 code frequency will be supplied to the section in the rear, from which it will feed over the defective joint and produce code following operation of the track relay with resultant display of the clear aspect by the associated signal.

The system provided by this invention is arranged so that on entrance of a train into a track section, if the train shunts the track relay for a period long enough to effect release of one of the auxiliary relays associated therewith, the other auxiliary relays will all become released quickly so that subsequent energization of the track relay will cause the lookout circuit to be established.

In the system shown in my application Serial No 210,743, on entrance of a train into a track section and shunting of the track relay the supply of energy to the FSA relay is interrupted, and after a short time interval the contacts of this relay become released. Release of the contacts of the FSA relay interrupts the supply of energy to theBSA relay and also interrupts the snubbing circuit for the BSA relay with the result that the contacts of the BSA relay become released very quickly after release of the contacts of the FSA relay.

Release of the contacts of the BSA relay interrupts the supply of current to the winding of the H relay and initiates release of the contacts of the H relay, while release of the contacts of the BSA relay completes the circuit for supplying energy of the code frequency to the adjacent section in the rear.

Because of the slow releasing characteristic of the H relay, the contacts of this relay do not release immediately upon interruption of the supply of current to the relay winding but remain picked up for a short time interval.

If the train is short, light weight and high speed, and if shunting conditions are poor, there is a possibility that an impulse of coded energy supplied at the entrance end of the section will feed to the track relay and cause the contacts thereof to become picked up even though the section is occupied.

If this occurs subsequent to the release of the contacts of the FSA relay and prior to the release of the contacts of the H relay, then on picking up of the contacts of the track relay energy is supplied to the winding of relay FSA and the contacts of this relay become picked up so that on release of the track relay contacts energy is supplied to the winding of the BSA relay. As a result the contacts of the BSA relay become,

picked up, and if this occurs prior to release of the contacts of the H relay the circuit for supplying energy of code frequency to the rear is complete.

As the train is assumed to be short and fast it will have advanced far enough in the track section to be ineffective to shunt the track relay with respect to energy feeding from the adjacent section in the rear, and on the supply of energy of 180 code frequency to the rear, the current feeds over the defective joint and causes code following operation of the track relay to thereby maintain all of the auxiliary relays energized with the result that the supply of energy of 180 code frequency is continued while the signal for the section displays its clear indication even though the section is occupied.

A similar condition results in the system shown in my application Serial No. 210,743 if on entrance of a train into a track section, an insulated joint becomes defective so that the equipment operates to establish the lockout circuit, and if immediately after the lookout circuit is established, that is, before the contacts of the H relay have become released, the supply of energy to the track relay is temporarily interrupted. The interruption in the supply of energy to the track relay may come about as a result of interruption of the lookout circuit, or it may be the result of interruption of the connection of the track relay winding with the track rails.

As explained above, in the system shown in application Serial No. 210,743, on entrance of a train into a track section, and shunting of the track relay, the FSA and BSA relays become released, while a short time interval must elapse after release of the contacts of relay BSA before the contacts of the H relay become released.

As a result of the release of the contacts of the FSA and BSA relays the circuit for supplying ener of the '75 code frequency to the adjacent section in the rear is established, and, as-, suming that an insulated joint became defective as a result of passage of the train, the impulses of energy of this code frequency will feed over the defective joint to the track relay of the occupied section. As the train is assumed to be short and fast, it will have quickly advanced beyond the point at which it is effective to shunt the track relay with respect to energy feeding over the defective joint and an impulse of the '75 code frequency will feed to the track relay and cause its contacts to become picked up.

As a result of picking up of the track relay contacts energy is supplied to the winding of the FSA relay and the contacts of this relay become picked up to thereby establish the lockout circuit to supply steady uncoded energy to the adjacent section in the rear, while this current feeding over the defective joint keeps the track relay contacts picked up.

However, if for any reason the supply of energy to the track relay is interrupted, the track relay contacts will become released, and since the contacts of the FSA relay are picked up, energy will be supplied to the winding of the BSA relay and the contacts of, this relay will become picked up to interrupt the lockout circuit. If at the time the contacts of the BSA relay become picked up the contacts of the H relay are still in their picked up position the circuit for'supplying energy of the 180 code frequency to the section in the rear will be complete, and this energy feeding over the defective joint will produce code following operation of the track relay as explained above.

The system provided by this invention operates in such. manner that on entrance of a train into av track section, and shunting of the track relay for a period long enough to effect release of the contacts of one of the auxiliary relays controlled thereby, the remaining auxiliary relays associated with the track relay will be quickly and positively caused to release their contacts to thereby insure that on subsequent picking up of the track relay contacts the lockout circuit will be established.

In the system provided by this invention, on entranceof a train into the track section [2T with resultant shunting of the track relay, the supply of energy to the winding of relay 12H is interrupted, and. after a time interval the contacts of the relay 12H become released. The release time of the relay I2H is substantially the same as that of the FSA relay in the system shown in, application Serial No. 210,743, since each relay must be sufficiently slow in releasing to bridge the longest off period in the code supplied to the relay.

On movement of the contact 24 of relay [2H out of engagement with its front point of contact, the. circuits for energizing the winding of relay I2FSA and for supplying energy to the primary winding of the decoding transformer I2DT are interrupted and each of these windings has a current induced therein. At this time, as explained above, the winding of the relay IZFSA and the lower portion of the primary winding 26 of the decoding transformer IZDT are connected in series and the currents induced in the two windings counteract each other so that the contacts of the relay I2FSA release almost instantaneously upon release of the contacts of the relay L2H.

On. release of thecontacts, of. relay LZFSA contact 2i interrupts both the circuit for supplying energy to the winding of relay IZBSA and the snubbing. circuit for the relay, and the contacts of this relay become released very soon after release of the contacts of the relay IZFSA. Since the contacts of the relays I2FSA and IZBSA release promptly, the time interval from release of the contacts of the relay IZH until the contacts of the relay I2BSA become released is relatively short, and there is, therefore, little time during which release of the relays might be interfered with by picking up of the track relay contacts as a result of the supply of an impulse of energy to the track relay from the forward end of the track section because of poor shunting conditions.

In addition, it will be seen that in the system provided by this invention that on release of the contacts of the relay IZH, which is the first relay in the series of auxiliary relays to release its con.- tacts on shunting of the track relay, contact 35 interrupts the circuit for supplying energy of code frequency to the section in the rear, and that thereafter energy is not supplied to the adjacent section in the rear until the contacts of the relay I2BSA become released, which is the last relay in the series of relays to become released.

Since energy is not supplied to the section in the rear during release of the auxiliary relays, there is no possibility that energy supplied to the adjacent section in the rear will feed over a defective joint and effect picking up of the track relay contacts with resultant interference with the release of the auxiliary relays.

When the contacts of the relay I2BSA become released contact 3'! establishes the circuit for supplying energy of the '75 code frequency to the adjacent section in the rear, and if an insulated joint separating sections HT and I2T is defective this energy will feed over the defective joint to the track relay IZTR. If at this time the train has advanced far enough in the track section [2T to be ineffective to shunt the track relay with respect to energy feeding to the track relay from the rear, or as soon as the train has advanced this far in the track section, an impulse of energy feeding from section HT to the winding of the track relay IZTR, eifects picking up of the track relay contacts.

On picking up of the track relay contacts energy is supplied to the winding of relay I2FSA over the circuit which includes front contact I6 of the track relay 12TH and back contact is of the relay IZBSA. As a result of the supply of energy to the winding of relay I2FSA the contacts of this relay become picked up and contact 38 establishes the lockout circuit to, supply steady energy to section HT, and this energy feeding over the defective joint maintains the contacts of the track relay IZTR picked up.

However, if for any reason the supply of en-- ergy to the track relay winding is interrupted immediately after establishment of the lookout circuit, the track relay contacts will become released, and as contact 2| of relay I2FSA is picked up, energy will be supplied to the winding of relay IZBSA over the circuit which includes back contact l6 of track relay IGTR. and front contact 2| of relay IZFSA. If the track relay remains in its released position for a period of time long enough to supply sufficient energy to the winding of relay IZBSA to cause thecontacts of the relay to become picked up, contact- 3.! of the relay will interrupt the lockout? cirw cuit so that energy will not be supplied to the track relay through the lookout circuit even if the fault which caused the interruption in the supply of current to the track relay winding is corrected. The track relay contacts will thereafter remain released, and after a brief time interval the contacts of the relay IZFSA will become released to thereby interrupt the circuit of the winding of relay IZBSA so that the contacts of this relay become released to initiate reestablishment of the lockout circuit.

It will be seen that under the conditions outlined above, at the time of picking up of the contacts of the relay IZBSA, the contacts of the relay IZH are released so that there is no possibility that the circuit for supplying energy of the 180 code frequency to the section in the rear will be established by picking up of the contacts of the relay IZBSA, and there is, therefore, no possibility that energy of this code frequency will be supplied to the adjacent section in the rear from which it would feed to the track relay of the occupied section with resultant interference with establishment of the lockout circuit, and possible improper display of a clear indication by the signal controlled by the track relay.

From the foregoing it will be seen that the system provided by this invention provides protection against improper operation of the equipment on passage of a light fast train.

In the system provided by this invention on shunting of the track relay for a period of time long enough to effect release of the first of the series of auxiliary relays associated with the track relay, the remaining relays of the series will quickly and positively release their contacts to thereby insure that the equipment will be in condition to establish the lockout circuit on picking up of the track relay contacts.

In addition, as the contacts of all of the auxiliary relays are released the circuit for supplying energy of the 180 code frequency to the section in the rear is interrupted in such manner that this circuit will not be established in the event the supply of energy to the track relay winding is momentarily interrupted immediately after establishment of the lockout circuit.

Operation of the equipment if the lockout circuit is improperly interrupted This system is also arranged so that if for any reason the lookout or steady energy supply circuit is improperly interrupted for a substantial time interval the circuit will be automatically reestablished.

For purposes of illustration it will be assumed that the lookout circuit for supplying steady uncoded energy to the winding of the transformer HT has been established, that the track section HT and the adjacent section in advance thereof are vacant, and that the lockout circuit is interrupted as a result of disconnection of a wire from the terminal of the transformer primary winding 30, or that the supply of current to the transformer primary winding 3!] is interrupted for some other reason, such as shorting of a wire.

As the supply of steady energy to the transformer primary winding is interrupted, no current is supplied to the rails of section HT and current no longer feeds over the defective joint to the relay IZTR.

Since it is assumed that at this time the section in advance of section IZT is unoccupied, coded energy of the 180 code frequency is supplied to the track rails of section iZT by the equipment associated with the adjacent section in advance, and this current feeds to the track relay IZTR.

On the first off period in the code subsequent to interruption of the supply of steady energy to the transformer IITT, the contacts of the relay IZTR become released and energy is supplied to the winding of relay IZBSA over the circuit which includes front contact 2| of relay IZFSA so that contacts of relay IEBSA become picked up.

On the next picked up period of the track relay contacts energy is supplied over the circuit which includes front contact it of relay IZBSA to the winding of relay IZH, while on picking up of the contacts of relay IZH energy is supplied to the winding of relay IZFSA, as explained above, and also to the primary winding 26 of transformer IZDT.

Since it is assumed that energy of the code frequency is supplied to the track relay IZTR at this time, the contact of relay I2J will become picked up and current will be sup-plied to the green lamp G of signal [25.

As the contacts of relays I'ZFSA, I ZFSB and IZI-I are picked up, the circuit for supplying energy of the 180 code frequency to the wire leading to transformer IITT is complete, but as it is assumed that the wire is not connected to primary winding 30 of transformer IITT, or that the wire is short circuited, energy is not supplied to the transformer, and, therefore, is not supplied by the transformer to the rails of section HT, while the signal for section HT will display its stop aspect.

Since at this time energy is not supplied to the rails of section HT, energy will not feed over the defective insulated joint from the rails of section HT to the relay I2TR, and this condition will continue as long as the wire is not connected to transformer winding 30 or is short circuited.

If the wire again becomes connected to the transformer primary winding 30, or if the supply of current to the transformer primary winding is reestablished in any other manner, impulses of current of the 180 code frequency will be supplied to the transformer and will be supplied by the transformer to the rails of section HT. The impulses of current supplied to the rails of section HT will feed over the defective joint to the track relay IZTR.

If at this time the impulses of energy supplied to section I IT are out of step with those supplied to section I2T, the impulses of current feeding over the defective joint from section HT will fill in the periods between the impulses of energy supplied to section IZT, and, as a result, the 'track relay IZTR will be energized all or substantially all of the time, and the contact N5 of the relay will not engage its back point of contact, or will engage it for such short periods of time that insufiicient energy will be supplied to the winding of relay IZBSA to maintain the contacts of that relay picked up.

If at the time the supply of energy to the transformer is reestablished the impulses of energy supplied to sections HT and HT are substantially in step with each other, they Will soon become out of step since the code transmitters which generate the code for the two sections are driven by separate motors which will not operate at exactly the same speed. Accordingly if the contacts of the track relay IZTR are not initially held in their picked up positions an abnormally large proportion of the time they soon will be as a result of the two codes becom ing out of step.

On release of the contacts of relay I2BSA contact I8 interrupts the circuit of the winding of relay I2H, while on movement of contact I8 of relay IZBSA into engagement with its back contact a circuit is established to maintain the Winding of relay IZFSA energized after contact 24 of relay IZH becomes released. The contacts of relay IZH do not release instantaneously upon release of contact I8 of relay I2BSA, and hence contact 24 of relay I2H maintains the circuit of the winding of relay IZFSA until after contact I8 of relay IZBSA engages its back contact to establish a circuit to supply energy to the winding of relay IZFSA. Accordingly the contacts of relay I2FSA are constantly picked up and contact 38 maintains the circuit shunting the '75 code contact of code transmitter IZC'I'.

On release of the contacts of relay IZBSA contact 31 interrupts-the circuit for supplying energy of 180 code frequency and engages its back contact with the result that the steady energy or lockout circuit is complete, and steady uncoded energy is supplied to the primary winding 30 of track transformer IITT, and this transformer supplies steady energy tothe rails of section I IT,

while the steady energy feeding over the defective insulated joint will maintain the contacts of track relay IZTR steadily picked up with the result that energy is continuously supplied over front contact It of the track relay to the winding of relay IZFSA to maintain-this winding energized.

On release of the contacts of relay L2H contact 24 interrupts the circuit for energizing the primary winding 26 of decoding transformer IZDT, while contact 32 engages its back contact to establish the circuit to illuminate the red or stop lamp R of signal IZS,

From the foregoing it will be seen that this system is arranged so that in the event that the lockout circuit is improperly interrupted this circuit will be automaticallyreestablished, and

that such reestablishment of the flockout circult does not depend upon more rapid release of the contacts of one auxiliary relay than of another. Instead the lockout circuit is automatically reestablished as soon as the contacts of the relay BSA become released, while, in, addition, as a result of the release of the contacts of this relay, a circuit is established to maintain the winding of relay FSA energized so that the contacts of relay FSA will be maintained picked up to thereby maintain the lookout circuit.

The operation of the equipment in the event the lockout circuit is improperly interrupted at a time when the section in advance of the defective joint is unoccupied having been explained, its operation if the section is occupied will now be considered.

front contact I6 of relay IZT'R to energize the winding of relay IZFSA. Atthis time the relays IZBSA and IZH are deenergized and theircontacts are released. I I

As the train is assumed to be present in the forward part of the track section IZT, the energy supplied to the rails of section I2T at the entrance end of the section is shunted from the relay I'2TR with the result that relay IZ TR is responsive only to current feeding'over the defective joint from section I IT;

When the lookout circuit is interrupted, as by shorting or disconnection of the Wire leading to winding 30, energy is no longer supplied to the rails of section HT and ceases to flow over the defective joint to energizethe relay I2TR and the contacts of this relaybecome released and establish the circuit of the winding of .relay IZBSA so that the contactsof this relay become picked up. The same sequence of operation follows if the track relay contacts become released as a result of disconnection or shorting of a wire connecting the track relay winding with the track rails. e

As a result of the release of the contacts of relay IZTR, the circuit for energizing the winding of relay IZFSA is interrupted and the contacts of this relay thereupon become released. On release of contactZI of relay IZFSA, the circuit of the winding of relay IZBSA is interrupted and the contacts of this relay become released, while release of contact 33 of relay IZFSAinterrupts the circuit shunting the 75 code contact of code transmitter IZCT, that is the lookout circuit, andenergy of the 75code frequencyis supplied to the wire leading to transformer I I TT.

Since it has been assumed that the lockout I At this time as the contacts of relay I2l-I are released, contact 32 establishes the circuit to illuminate the red or stop lamp R, and since because of the fault in the system no energy is supplied to the rails of section III, the signal for that section is conditioned to display its stop aspect.

The apparatus remains in this condition as long as the supply of energy to the transformer IITT or to the winding of the track relay IZTR. is interrupted. If, however, the supply of energy to the transformer or to the track relay is restored, then on the first impulse of current of the code frequency supplied to the transformer IITT, and feeding over the defective joint to the track relay IZTR, the contacts of relay I2TR. will be picked up and contact IE will engage its front contact to establish the circuit to supplycurrent to the Winding of relay IZFSA. As a result the contacts of relay IZFSA willbecome picked up and contact 38 will reestablish the lockout or steady energy supply circuit to supply steady uncoded energy to the transformer II'I'I. This steady energy feeding over'the defective joint to the relay IZTR. will maintain the contacts of relay I2'I'R constantly picked up so that current will be supplied over front contact I6 of. relay I ZTR. to steadily energize the winding of relay IZFSA, and contact 38 will be held picked up and will maintain the lookout circuit.

If an insulated joint becomes defective at a 75 time when the track stretch is unoccupied, the

impulses of coded energy supplied to section IIT and feeding over the defective insulated joint will combine with the impulses of energy supplied to section [2T and will cause the contacts of relay IZTR to remain picked up an abnormally large proportion of the time.

As a result of the increase in the time during which the contacts of the track relay IZTR are maintained picked up, the degree of energization of the winding of relay IZBSA is reduced to a value such that the contacts of this relay become released. On release of the contacts of this relay contact I8 establishes the circuit to supply energy to the winding of relay IZFSA so that .the contacts of that relay are maintained picked up, while on release of contact 31 of relay IZBSA the circuit for supplying energy of the 180 code frequency to transformer IITT is interrupted and the lockout or steady energy supply circuit for supplying steady uncoded energy to the track transformer IITT is established, and thissteady energy feeding over the-defective joint. to the track relay lZTR will thereafter maintain the contacts of the track relay picked up.

In addition on release of the contacts of the relay IZBSA contact l8 interrupts the circuit of the winding of relay IZH with the result that the contacts of that relay become released and contact 32 establishes the circuit to illuminate the red or stop lamp R of signal IZS.

From the foregoing it will be seen that the system provided by this invention provides an improved lockout circuit which is positive in operation, and which is arranged so that if the lookout circuit is improperly interrupted, it will be automatically reestablished as soon as the supply of energy to the section in the rear of the defective joint is resumed.

It will be seen also that this system is arranged to minimize current consumption since the supply of energy to the primary winding of the decoding transformer is controlled by a contact of auxiliary relay H. The contacts of relay H become picked up to establish the circuit to supply energy to the transformer primary winding only when the track relay is responding to coded energy. This prevents the supply of energy to the decoding transformer primary winding at times when the section is occupied or when the lockout thereby eliminates current consumption by the transformer at such times.

While the current consumption by the transformer primary winding when the track relay contacts are not responding to coded energy is not large, it is advantageous to eliminate this needless current consumption, particularly where batteries are depended upon as a source of supply of current.

In the system shown in this application the primary winding of the decoding transformer is employed to provide an inductive discharge to matchthat of the winding of the relay FSA, but it should be understood that the controlled energization of the transformer primary winding may be employed without this feature if desired.

Likewise the controlled energization of the primary winding of the decoding transformer is not restricted to use in signaling systems incorporating the lockout circuit, and may be employed in any coded signaling system.

Similarly it shouldbe understood that if the inductive discharge to match that of the relay FSA is desired, it may be provided by a separate circuit is established, and

independent inductive winding, such as a reactor, instead of employing the transformer primary Winding for this purpose.

It will be seen also that this system is arranged so that on shunting of the track relay of a section the auxiliary relays associated with that track relay are deenergized serially, and that the first auxiliary relay in the series to release its contacts interrupts the supply of energy to the adjacent section in the rear, while energy cannot thereafter be supplied to the section in the rear until the last relay in the series releases its contacts. This prevents the supply of energy to the adjacent section in the rear during the release of the contacts of the auxiliary relays, and eliminates the possibility that such energy will feed over a defective insulated joint and produce code following operation of the track relay so as to interfere with completion of the release of the entire series of auxiliary relays.

Although I have herein shown and described only one form of railway signaling system embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails separated by insulated joints into successive track sections including a forward and a rearward section, means for at times supplying coded or periodically interrupted energy to the rails of said forward section, a code following track relay having a winding receiving energy from the rails of said forward section, a signal governing traffic in said forward section capable of displaying a plurality of different indications, means governed by said track relay for controlling said signal in such manner that the signal displays a proceed indication when and only when said relay is responding to coded energy and displays its most restrictive indication when the track relay is not responding to coded energy, a first, a second and a third auxiliary relay, a circuit including a front contact of the track relay for supplying energy to the winding of the first auxiliary relay, a circuit including a back contact of the track relay and a front contact of the first auxiliary relay for supplying energy to the winding of the second auxiliary relay. a circuit including front contacts of the track relay and of the second auxiliary relay for supplying energy to the winding of the third auxiliary relay, a circuit including a front contact of the third auxiliary relay for supplying energy to the winding of the first auxiliary relay, a circuit including a back contact of an auxiliary relay for supplying coded energy to the rails of said rearward section, a circuit including a front contact of the first auxiliary relay and a back contact of one of the other auxiliary relays for supplying steady energy to the rails of said rearward section, and a circuit including a front contact of the third auxiliary relay for supplying coded energy to the rails of said rearward section.

2. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails separated by insulated joints into successive track sections including a forward and a rearward section, means for at times supplying coded or periodically interrupted energy to the rails of said forward section, a code following track relay having a winding receiving energy from the rails of said forward section, a signal governing trafiic in said forward section capable of displaying a plurality of different indications, means governed by said track relay for controlling said signal in such manner that the signal displays a proceed indication when and only when said relay is responding to coded energy and displays its most restrictive indication when the track relay is not responding to coded energy, a first, a second and a third auxiliary relay associated with said track relay, a circuit including a front contact of the track relay and a back contact of the second auxiliary relay for supplying energy to the winding of the first auxiliary relay, a circuit including a back contact of the track relay and a front contact of the first auxiliary relay for supplying energy to the winding of the second auxiliary relay, a circuit including front contacts of the track relay and of the second auxiliary relay for supplying energy to the winding of the third auxiliary relay, a circuit including a front contact of the third auxiliary relay for supplying energy to the winding of the first auxiliary relay, a circuit including a back contact of one of the auxiliary relays for supplying coded energy to the rails of said rearward section, a circuit including a front contact of the first auxiliary relay and a back contact of one of the other auxiliary relays for supplying steady energy to the rails of said rearward section, and a circuit including a front contact of the third auxiliary relay for supplying coded energy to the rails of said rearward section.

3. In a coded railway signaling system, in com- 'bination, a stretch of railway track having a pair of track rails separated by insulated joints into successive track sections including 'a forward and a rearward section, means for at times supplying coded or periodically interrupted energy to the rails of said forward section, a code following track relay having a winding receiving energy from the rails of said forward section, a signal governing traffic in said forward section capable of displaying a plurality of different indications, means governed by said track relay for controlling said signal in such manner that the signal displays a proceed indication when and only when said relay is responding to coded energy and displays its most restrictive indication when the track relay is not responding to coded energy, a first, a second and a third auxiliary relay associated with said track relay, means operative on initiation of code following operation of the track relay contacts for supplying energy to the winding of the first auxiliary relay on a movement of the track relay contacts to their picked up position, means operative on a movement of the track relay contacts to their released position subsequent to picking up of the contacts of the first auxiliary relay for supplying energy to the winding of the second auxiliary relay, a circuit including front contacts of the track relay and of the second auxiliary relay for supplying energy to the winding of the third auxiliary relay, a circuit complete when the contacts of the third auxiliary relay are picked up to supply energy to the winding of the first auxiliary relay to thereby insure that on shunting of the track relay the contacts of the first auxiliaryrelay will remain picked up until the contacts of'the third auxiliary relay become released, a circuit including a back contact of one of said auxiliary relays for supplying coded'energy to the rails of said rearward section, a circuit including a front contact of the first auxiliary relay and a back contact of the second auxiliary relay for supplying steady energy to the rails of said rearward section, and a circuit including a front contact of the third auxiliary relay for supplying coded energy to the rails of said rearward section.

4. In a coded railway signaling system, in com bination, a stretch of railway track having a pair of track rails divided by insulated joints into a forward and a rearward section, means governed by traffic conditions in advance of said forward section for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy from the rails of said forward section, said track relay having associated therewith a first, a second and a third auxiliary relay, a circuit including a front contact of the track relay and a back contact of the second auxiliary relay for energizing the winding of the first auxiliary relay, a circuit including a front contact of the third auxiliary relay for also energizing the Winding of the first auxiliary relay, a circuit including a back contact of the track relay and a front contact of the first auxiliary relay for energizing the winding of the sec- 0nd auxiliary relay, a circuit including front contacts of the track relay and of the second auxiliary relay for energizing the winding of the third auxiliary relay, a circuit including a back contact of one of said auxiliary relays for supplying coded energy to the rails of said rearward section, a circuit including a front contact of the first auxiliary relay and a back contact of the second auxiliary relay for supplying steady energy to the rails of said rearward section, and a circuit including front contacts of said first and third auxiliary relays for also supplying coded energy to the rails of said rearward section.

5. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a forward and a rearward section, means governed by traffic conditions in advance of said forward section for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy from the rails of said forward section, said track relay having associated therewith a first, a second and a third auxiliary relay, a circuit including a front contact of the track relay and a back contact of the second auxiliary relay for energizing the winding of the first auxiliary relay, a circuit including a front contact of the third auxiliary relay for also energizing the winding of the first auxiliary relay, a circuit including a back contact of the track relay and a front contact of the first auxiliary relay for energizing the winding of the second auxiliary relay, a circuit including front contacts of the track relay and of the second auxiliary relay for energizing the winding of the third auxiliary relay, a snubbing resistor operative when shunted across the terminals of the winding of the first auxiliary relay to render the contacts of said relay slow in releasing, a circuit including a back contact of the third auxiliary relay for connecting said snubbing resistor across the terminals of said first auxiliary relay winding, a circuit including a back contact of one of said auxiliary relays for supplying coded energy to the rails of said rearward section, a circuit including a front contact of the first auxiliary relay and a back contact of the second auxiliary relay for supplying steady energy to the rails of said rearward section, and a circuit including front contacts of said first and third auxiliary relays for also supplying coded energy to the rails of said rearward section.

6. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a forward and a rearward section, means governed by traffic conditions in advance of said forward section for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy from the rails of said forward section, said track relay having associated therewith a first, a second and a third auxiliary relay, a circuit including a front contact of the track relay and a back contact of the second auxiliary relay for energizing the winding of the first auxiliary relay, a circuit including a front contact of the third auxiliary relay for also energizing the winding of the first auxiliary relay, a circuit including a back contact of the track relay and a front contact of the first auxiliary relay for energizing the winding of the second auxiliary relay, a circuit including front contacts of the track relay and of the second auxiliary relay for energizing the winding of the third auxiliary relay, a first snubbing resistance operative when shunted across the terminals of the Winding of the first auxiliary relay to render the contacts of said relay slow in releasing, a circuit including a back contact of the third auxiliary relay for connecting said first snubbing resistance across the terminals of said first auxiliary relay winding, a second snubbing resistance, means operative during movement of the contacts of the third auxiliary relay between their released and picked up positions to connect the first and second snubbing resistances in series across the terminals of the first auxiliary relay winding to thereby prevent release of the contacts of said first auxiliary relay during move ment of the contacts of the third auxiliary relay from their released to their picked up positions, a circuit including a back contact of one of said auxiliary relays for supplying coded energy to the rails of said rearward section, a circuit including a front contact of the first auxiliary relay and a back contact of. the second auxiliary relay for supplying steady energy to the rails of said rearward section, and a circuit including front contacts of said first and third auxiliary relays for also supplying coded energy to the rails of said rearward section.

'7. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a forward and a rearward section, means governed by trafiic conditions in advance of said forward section for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy from the rails of said forward section, said track relay having associated therewith a first, a second and a third auxiliary relay, a circuit including a front contact of the track relay and a back contact of one of the auxiliary relays other than the first auxiliary relay for supplying energy to the winding of the first auxiliary relay to pick up the contacts of said relay, means responsive to code following operation of the track relay contacts for supplying energy to the winding of the first auxiliary relay to maintain the contacts of said relay picked up, a circuit including a back contact of the track relay and a front contact of the first auxiliary relay for energizing the second auxiliary relay, a circuit including front contacts of the track relay and of the second auxiliary relay for energizing the third auxiliary relay, a circuit including a back contact of one of said auxiliary relays for supplying coded energy to the rails of said rearward section, a circuit including a front contact of the first auxiliary relay and a back contact of the second auxiliary relay for supplying uncoded energy to the rails of said rearward section, and a circuit including front contacts of two of said auxiliary relays for supplying coded energy to the rails of said rearward section.

8. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails separated by insulated joints into successive track sections including a forward and a rearward section, means for at times supplying coded or periodically interrupted energy to the rails of said forward section, a code following track relay having a winding receiving energy from the rails of said forward section, a signal governing traffic in said forward section capable of displaying a plurality of different indications, means governed by said track relay for controlling said signal in such manner that the signal displays a proceed indication when and only when said relay is responding to coded energy and displays its most restrictive indication when the track relay is not responding to coded energy, a first, a second and a third auxiliary relay associated with said track relay, a circuit including a front contact of the track relay and a back contact of one of the auxiliary relays other than the first auxiliary relay for supplying energy to the winding of the first auxiliary relay to pick up the contacts of said relay, a circuit including a back contact of the track relay and a front contact of the first auxiliary relay for supplying energy to the winding of the second auxiliary relay, a circuit including front contacts of the track relay and of the second auxiliary relay for supplying energy to the winding of the third auxiliary relay, an inductive winding, a circuit connecting said inductive winding and the winding of the first auxliary relay in series, a circuit complete when the contacts of the third auxiliary relay are picked up for energizing said inductive winding and the winding of the first auxiliary relay in parallel, whereby the contacts of the first auxiliary relay are maintained picked up as long as the contacts of the third auxiliary relay are picked up and whereby on release of the contacts of the third auxiliary relay the energizing circuits of the inductive winding and of the first auxiliary relay winding are interrupted, said inductive winding and said first auxiliary relay winding being proportioned so that the currents induced therein on interruption of the supply of energy thereto substantially offset each other to thereby insure prompt release of the contacts of the first auxiliary relay on release of the contacts of the third auxiliary relay, a circuit including a back contact of one of said auxiliary relays for supplying coded energy to the rails of said rearward section, a circuit including a front contact of the first auxiliary relay and a back contact of one of the other auxiliary relays for supplying steady energy to HOWARD A. THOMPSON. 

